1. Field of the Invention
The present invention relates generally to a mobile communication system. More particularly, the present invention relates to a method and apparatus for controlling an operation of a User Equipment (UE) when the UE enters into a forbidden registration area and controlling measuring the frequency of the forbidden registration area.
2. Description of the Related Art
A 3rd Generation (3G) mobile communication system operating in Wideband Code Division Multiple Access (WCDMA) based on the European Systems, Global System for Mobile communications (GSM) and General Packet Radio Services (GPRS) in compliance with the 3rd Generation Partnership Project (3GPP) standards, and Universal Mobile Telecommunication System (UMTS) provides a uniform service of sending packetized text, digital audio and video, and multimedia data at high rates of 2 Mbps or above to mobile phone users or computer users irrespective of time and location.
In UMTS, a radio access network called UMTS Terrestrial Radio Access Network (UTRAN) connects UEs to another network over a Core Network (CN) composed of a Circuit Service or Circuit-switched Service (CS) domain and a Packet Service or Packet-switched Service (PS) domain. The entire service area of the UMTS system is divided into a plurality of registration areas such as Location Areas (LAs) and Routing Areas (RAs). An LA is a registration area unit for a CN node in the CS domain, and an RA is a registration area unit for a CN node in the PS domain.
FIG. 1 depicts registration areas in a conventional 3GPP system. Referring to FIG. 1, an LA or RA (LA/RA) may be comprised of cells belonging to a Radio Network Controller (RNC) connected to a CN node. Each LA/RA is handled by one CN node only and a plurality of LAs/RAs may belong to one CN node.
A CN node called Mobile Switching Center (MSC) manages an LA in the CS domain, and a CN node called Serving GPRS Supporting Node (SGSN) manages an RA in the PS domain. When a UE moves to a new LA/RA, the UE registers to the LA/RA by LA Update (LAU)/RA Update (RAU). Then the UE does not need to perform LA/RA registration in case of inter-cell movement within the LA/RA. The LA/RA is defined logically as well as geographically. That is, each registration area can be defined as a geographical area using a predetermined frequency band.
The CN node detects the LA/RA of the UE by the LA/RA registration procedure. If the UE is in idle mode, the CN node pages the UE based on information about the LA/RA of the UE. The idle mode is a mode without a Radio Resource Control (RRC) connection between the UE and the RNC. The idle-mode UE determines whether it is paged by monitoring a Paging Indicator CHannel (PICH), considering an efficient power mode. The paging is a message or a procedure that indicates call incoming for the UE.
Although an LA/RA has a plurality of cells under a particular CN node as illustrated in FIG. 1, this configuration may vary depending on the cell/registration area operating strategy of an operator. While the LA/RA is a registration area unit for the CN node, a UTRAN Registration Area (URA) is a registration area unit for an RNC controlling the radio interface of the UE. The RNC may manage particular UEs on a URA basis.
When the UE moves to a new LA/RA and thus performs LAU/RAU, the CN node of the new LA/RA can reject the LA/RA registration of the UE. For example, if a GSM terminal supporting GSM only enters a UMTS LA/RA, the CN node of the LA/RA can reject the GSM terminal's registration to the LA/RA in order to ensure UMTS service to UMTS terminals.
Nonetheless, the UE conventionally measures the radio strengths of cells within a forbidden registration area for cell reselection, although it is forbidden from registration to the forbidden registration area. As a consequence, the UE dissipates power and cell selection/reselection is rendered inefficient because the UE is forbidden from registering to cells belonging to the forbidden registration area irrespective of the measurement results.
Accordingly, there is a need for an improved method and apparatus for controlling a User Equipment's measuring within a forbidden registration area.